In the second (2G) and third generation (3G) mobile telephone communication systems, distinct switching domains can be identified within the core networks that service user terminals. These domains typically include the circuit-switched (CS) service domain and the packet-switched (PS) service domain. In the CS domain, signals are physically routed to their destination through a unique connection, whereas in the PS domain individual packets are dynamically routed to the appropriate destinations based on a destination address associated with each packet.
2G and 3G user terminals typically access the core network via a CS access network, i.e. via the CS domain. The CS network access requires that depending on the domain where a particular service will be eventually be performed, there might be a need for switching from the CS access domain to a PS or any other service domain. This implies that a service domain selection has to be performed somewhere in the connection from the user terminal to the core network.
Various service domain selection approaches have already been proposed. In one exemplary service domain selection procedure described in U.S. Pat. No. 6,567,667 B1, service domain selection is performed by the user terminal. More specifically, the user terminal is configured to construct messages which specify one of the CS service domain and the PS service domain for a particular service requested by the user terminal. The domain selection performed within the user terminal is based inter alia on service information received from the network.
The approach of having the service domain selected by the user terminal requires the implementation of a specific decision logic within each user terminal. This means that older user terminals that do not support this decision logic will be barred from service domain selection.
It would thus be beneficial to move the service domain selection procedure from the user terminal to the network side. In this regard, U.S. Pat. No. 6,567,667 B1 proposes two different mechanisms. A first network-based selection mechanism allows an access network to override the service domain selection requested by a user terminal. According to a second mechanism, the access network autonomously selects the service domain when a mobile terminal initiates a communication session without specifying a particular domain. The service domain selection performed by the access network is essentially based on a mapping scheme configured by a network operator. In this mapping scheme, each service is mapped to a particular domain. Depending on the service requested by the user terminal, the access network can thus autonomously select the appropriate service domain by consulting the mapping scheme.
While a network-based mapping scheme can easily be configured by the network operator and does not require any modifications on the terminal side, it also has some drawbacks. First, the autonomous nature of the network-based selection procedure prevents users from influencing the service domain selection procedure. Second, the approach of controlling domain selection via a dedicated mapping scheme is a concept that does not fit very well into the existing network environments.
Accordingly, there is a need for a service domain selection technique that seamlessly integrates into the existing networks.